also: あねさん
noun
Respectful or familiar noun/title for an older sister. This sense is usually written 姉さん; it is softer and more address-like than plain 姉.
姉さんに宿題を手伝ってもらった。
I had my older sister help me with my homework.
Sis, are you free tomorrow?
noun
Vocative use for addressing a young woman. Without お, it can sound familiar, casual, old-fashioned, or slightly rough depending on the speaker and situation.
姉さん、これ落としましたよ。
Miss, you dropped this.
noun
Used to address or refer to a waitress, hostess, or woman serving customers, especially in older or more rough-and-ready settings. This use is usually written 姐さん.
姐さん、熱燗を一本お願いします。
Miss, one hot sake, please.
noun
ma'am; senior woman
Specialized use in the geisha world: a geisha may use 姐さん for a senior woman or superior. This sense is usually written 姐さん.
新人の芸者は姐さんに作法を教わった。
The new geisha learned the proper etiquette from her senior.